Battery cells within a vehicle battery pack may exhibit different characteristics. For instance, battery cells located in one part of the battery pack may be subject to different temperatures than those located in a different area of the pack. These and other factors may, in turn, affect the individual cell voltage, current, resistance, state-of-charge (SOC), state-of-health (SOH) and/or other battery cell conditions over time, and can lead to discrepancies between the battery cells so that they are not identical. Another potential source of battery cell discrepancy involves limitations in the manufacturing process, as such a process is not always capable of producing battery packs having perfectly identical cells.
It is usually desirable to maintain a battery pack such that the cell voltages and/or other battery cell conditions are balanced and evenly distributed across the pack; some cell balancing techniques have been developed for this purpose. One such technique involves discharging battery cells that have become overcharged, however, this type of technique may result in a loss of efficiency since some electrical energy is wasted in the discharging process.